Motivation

IEP-43 introduces persistent caches snapshots feature. This feature highly adopted by Ignite users.

In-memory caches snapshots will simplify the following use-cases:

• In-memory cluster restarts.
• Version upgrade.
• Disaster recovery.
• DC/Hardware replacement.
• Data motion.

Description

in-memory snapshots will resuse existing snapshot code when possible. So key design decisions stay the same. It assumed that reader knows and understand IEP-43. So design description will focus on difference on persistence and in-memory snapshot.

1. PME + Checkpoint guarantees to make sure of visibility of all dirty pages:

Only PME required for in-memory snapshots. We can set write listener during PME because no concurrent transactions allowed.

2. Persistent pages contains CRC to make sure data integrity while storing on disk.

CRC for each page must be calculated and written to snapshot metadata during snapshotting.

CRC must be checked during restore. 

3. Metadata.

• StoredCacheData.
• binary_meta
• marshaller

must be properly prepared and saved during snapshot.

Risks and Assumptions

DataRegionConfiguration#persistenceEnabled=false  for in-memory caches by the definition.

The same value must be for DataRegionConfiguration when cache group restored from in-memory snapshot.

Discussion Links

// Links to discussions on the devlist, if applicable.

Reference Links

• IEP-43: Cluster persistent caches snapshots

Tickets